Insurance Operations - Reinsurance Ceded and Assumed (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Written premiums
Direct written premiums	$ 964,512	$ 889,526	$ 833,536
Assumed from other companies	3,499	5,586	2,798
Ceded to other companies	115,871	45,038	276,048
Net written premiums	852,140	850,074	560,286
Earned premiums
Direct earned premiums	918,718	844,234	788,862
Assumed from other companies	3,887	10,266	2,477
Ceded to other companies	114,751	123,715	181,553
Net premiums earned	$ 807,854	$ 730,785	$ 609,786
Percent of amount assumed to net	0.50%	1.40%	0.40%
Losses and loss adjustment expenses incurred
Direct net losses and loss adjustment expenses incurred	$ 556,051	$ 485,770	$ 483,209
Assumed from other companies	9,298	(3,209)	720
Ceded to other companies	64,324	47,731	90,188
Net losses and loss adjustment expenses incurred	$ 501,025	$ 434,830	$ 393,741